At the present time, many compound materials, such as indium arsenide (InAs), gallium antimonide (GaSb), aluminum antimonide (AlSb), aluminum arsenide (AlAs) and the like are utilized in the formation of heterojunction transistors, generally referred to as a heterojunction FET (field effect transistor) or simply a HFET. InAs/GaSb/AlSb based heterojunction devices show great promise for electronic applications. The InAs channel FET with AlSb or AlGaSb barriers has a very high mobility (.perspectiveto.33,000 cm.sup.2 /V-s) and saturation velocity for electrons, while the GaSb channel has a high mobility (.perspectiveto.1000 cm.sup.2 /V-s) and high saturation velocity for holes.
In order to take full advantage of this technology, for highly integrated digital ICs, a process for integration of n and p channel complementary devices is required. In standard complementary HFET technology, which is based on GaAs or InP, the magnitude of the source and drain access resistance are reduced by implanting donors or acceptors using the gate metal (e.g. titanium tungsten nitride, TiWN) as a mask. However, in some of the compound materials mentioned above, implanting impurities causes swelling of the implanted regions of the material. This swelling affects the electrical properties of the device and is known to be a major problem in the use of some compound materials for complementary FETs and the like.
It is a purpose of the present invention to provide a new and improved method of fabricating HFETs, and especially complementary HFETs, from compound semiconductor materials.
It is another purpose of the present invention to provide a new and improved method of fabricating HFETs, and especially complementary HFETs, from compound semiconductor materials without requiring implanting and the like.
It is another purpose of the present invention to provide new and improved HFET devices, and especially complementary HFETs, from compound semiconductor materials with no implants or the like.